Static and fluid velocity seal, method and apparatus



Aug. 10,1926. 1,595,481

- O. MINTON STATIC AND FLUID VELOCITY SEAL, METHOD AND APPARATUS Original Filed Nov. 30. 1920 ATTORNEY Fatented' Aug 10, 1926.

OGDEN MINTON, OF'GREENXVICH, CONNECTICUT.

STATIC AND FLUID VELOCITY SEAL, METHOD AND APPARATUS.

Original application filed November 30,1920, Serial K0 421 136. Divided and this application filed January 20, 1922, Serial No. 530,666. Renewed February 17, 1926.

This application is a division of my copending application Ser. No. 427,436, -flled November 30, 1920, Case L.

My invention relates to the method of treating materials in a vacuum, and more particularly to the method of protecting the openin or openings into the vacuum chamber, tirough which opening or openings the material to be treated is introduced and withdrawn from the chamber githout breaking the vacuum in the cham- My invention relates more particularly to a vacuum seal maintained by the application of static and .velocityhead, i. e. the difference in pressure between the atmosphere and vacuum being balanced by the static and velocity head of the sealing medium. Through this seal the material to be treated in the vacuum chamber is passed in any suitable manner.

My invention further relates moreparticularly to the method of drying sheet material, as a continuous web of paper either coming from the wet end of a paper machine, or from a sizing vat, or from a coloring apparatus, coating machine or printing machine or directly from a roll of Wet paper.

My invention further relates to a Vacuum apparatus including a vacuum chamber having passages extending from the said vacuum cham er and open to the atmosphere. These passages are protected by static and velocity fluid seals which prevent the admission of air into said vacuum chamber certain elements and. combinations of elements, whereby the method or processes herein described may be carried out, as well as to certain details of construction, all of which will be more fully hereinafter de scribed in the specification and pointed out in the claims.

The figure is a vertical section through a portion of a vacuum chamber equipped with my invention.

The vacuum chamber A has a vacuum maintained therein in any suitable manner. I have shown the vacuum chamber equipped with one of my static and velocity fluid seals, though of course it is to be understood that a similar seal may be employed at the metric seal 10.

exit end of the vacuum chamber, or any other formof velocity fluid seal may be used, such as shown for example in my parent application, Ser. No. 427,436.

The felt roll housing 2 is connected with a vertical passage?) having a restricted area 4. This passage 3 opens into the vacuum chamber A. within which are mounted one or more drying drums or cylinders 5 as shown for example in my parent application.

I use any suitable fluid for my static velocity fluid seal 6 which has no affinity for or deleterious effect upon the sheet material to be dried. If mercury, or other similar material be used as the fluid of my seal, it will fill the felt roll housing 2, reaching the level 7 on the surface exposed to the atmosphere and the level 8 in the passage 3. The height in the passage 3, of course, will depend on the degree of vacuum maintained in the vacuum chamber A.

The mercury, or similar materialfforming the fluid of the static and velocity fluid seal passes through the restricted area 4 and through the pipe 9 into the barometric seal 10. The suction pipe 11 of the pressure pump 12 withdraws the fluid from the baro- The end of the suction pipe 11 is arranged above the end 13 of the pipe 9 so that it will be impossible for the pump 12 to break thebarometric seal by momen tarily, or accidently, Lwithdrawing much of the fluid from the barometric seal 10. The pressure pump 12 is driven in any suitable manner as by the motor 14 and forces the fluid of the seal through the pipe 15 into the felt roll housing 2 beneath the roll 16.

The height of the column of mercury or similar fluid in the passage 3 may be varied.

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Assuming for example that the vacuum maintained in the vacuum chamber A is 28" of mercury, and the column of mercury in the passage 3 is 18", this column of mercury, or similar material acts as a static head and reduces the amount of fluid which has to be pumped by the pump 12 to maintain the protectin seal for the vacuum chamber.

With t 1e apparatus arranged as above described and with 18 of mercury or similar material in the passage 3, thiscolumn of mercury balances 18" of vacuum in the vacuum chamber A. As the vacuum malntamed in the vacuum chamber, is, for example, 28"

there will be a difference of only 10" which will have to be overcome or compensated for by the pump 12, pumping the fluid through the restricted passage 4 and around through the barometric seal 10, suction pipe 11, pump 12, and pipe 15. In other words, the pump instead of pumping the fluid of the seal at a velocity sutlicient to balance the vacuum of 28", will, with this static head of mercury, only have to pump the fluid of the seal at suflicient velocity to balarice a vacuum of 10 of mercury. Of course different degrees of vacuum and di ft'erent. static heads maybe employed without departing from my 111- vent-ion. seal 10 with relation to the level of the over- .fiow 8 may vary with the particular degree of vacuum employed in the vacuum chamber.

For example, when the vacuum is 28 the seal 10 will be so located that the level of the mercury then will be more than-twentyeight inches below the level 8 of the overflow. Preferably the 'seal 10 is so located that it will operate with any vacuum maintained .in the vacuum chamber.

I have shown the passage 3, by way of example, arranged at right angles to the horizontal.

My invention is particularly adapted to be used in connection with drying sheet material in the form of paper, though it is to be distinctly understood that 'it is equally applicable to and covers drying sheet material. in the form of textile fabrics, as for example, drying such fabrics after they have been washed or bleached or dyed, or otherwise treated b a liquid of some description.

The wet we of paper 17 coming directly from the wet end of a paper machine. or from a coloring apparatus, coating machine, printing machine, or directly from a roll of wet paper is fed into the vacuum chamber A through the static and velocity fluid seal 6, through the felt roll housing 2 under the guide roll 16, through the passage 3 and restricted passage 4 and thence into the vacuum chamber A and preferably over one or more drying drums or cylinders 5, as shown for example in my parent application above referred to. .After the web 1'? is dried in the vacuum chamber A it'is passed out of said vacuum chamber either through a duplicate static and velocity fluid seal, such as just described, or through any one of the velocity fluid seals shown in my said parent application. It is, of course, to be understood that in some cases I may use felts as shown in my said parent application Ser. No. 427,436, of which this is a division.

My method possesses many advantages not present in processes heretofore used for n any years in the drying of paper.

The evaporation process, which is characteristic of the so-called loft drying of paper, has many fully recognized disadvantages,

The level of the mercury in theany yet it is used today and has been in use for many years. In this method the wet paper is taken from the paper machine, cut into sheets, hung on-poles, carried to the drying room where it is subjected to hot air at about 130 F. for about 4:8 hours, and when dry, each sheet is separately calendered. Although possessing the advantage of drying at a comparatively low temperature, whereby the moisture is slowly evaporated, loft drying is obviously very inefficient and costly, because it requires many separate manipulations, is extremely slow, uses extensive floor space and wastes heat.

The process which is employed in the ordinary paper machine in common use, is likewise subject to many disadvantages. In such machine, the wet paper as it comes from the paper machine, is passed over many revolving cylinders, heated internally by steam to sufficiently high degree of heat to raise the temperature of the water in the paper to 212 F-., the atmospheric boiling point of water. It is customary to supply the drying cylinders with steam at approximately 5.3 pounds gauge pressure, at which the steam has a temperature of 228 F. giving a difference of temperature (228212) of only 16 F. With this slight difference of temperature the transfer of heat is extremely slow, and hence it is necessary to employ many drying cylinders, in board machines often one hundred, and in news print machines, forty or more.

Also due to convection and conduction losses, as well as those those incident to leaks in the piping system and other inefhciencies, the heat actually required for atmospheric drying of a ton of wet paper, is very much in excess of the theoretical requirement. The thermal efficiency of atmospheric drying by steam heated cylinders is therefore very low. Furthermore, the steam produced .from boiling the water out of the paper, is driven off into the operating room, and although fans and exhausters are employed, at large expense for power and maintenance, the room atmosphere is constantly saturated with moisture so as to rust and ultimately destroy' all iron and steel materials, and produces an exceedingly disagreeable and unhealthy atmosphere in which to work. It is well known that the minimum temperature 212, the atmospheric boiling point of water, is positively injurious to, and results in oxidizing, the fibres of the paper, the strength of which is vastly improved when the paper is dried at lower temperatures, as in loft drying. This atmospheric drying process requires large initial cost for cylinders, felts and other necessary equipment. and extensive floor space, and results in the consumption of large amounts of power, and

, great cost for operation, maintenance and repairs.

In my improved vacuum drying method I contemplate maintaining within the chamber a vacuum of about 28 of mercury, in which water boils at 100 F., and supplying the drying cylinders with steam at 5.3 pounds gauge pressure,producing a temperature of 228 F. The temperature difference between the temperature of the steam in the cylinders and that of the paper, is therefore, 128 F. in my vacuum method, or 8 times greater (16 F. X 8:128 F.) than the temperature difference in atmospheric drying. In my improved method the paper dries approximately 8 times faster than in atmospheric drying, and I require only about one-eighth the number of drying cylinders to dry paper at the same rate of speed. I am able to dry paper ,with 5 cylinders in the same time required of 40 cylinders drying at atmospheric pressure, resulting in great economies in cost'of the machine, floor space and of necessary piping, felts, auxiliary equipment, and particularly in power and maintenance charges.

The thermal efli ciency of my 1 vacuum method is very much greater than that of the atmospheric cylinder drying heretofore in universal use for drying paper. Theoretically, it requires about 4287 pounds of steam to dry one ton of paper at atmospheric pressure, but to compensate for convection and conduction losses, and those due to leaks in the piping system, and other inefliciencies, it has been shown in practice that about 10,600 pounds are required.

In my method, using a vacuum of about 28", the convectiomconduction and piping losses are exceedingly small and the total steam required to dry a ton of paper by my method is approximately 5200 pounds.

It is an established fact that paper dried at low temperatures is much stronger than when it is dried at the high temperatures used in paper machine atmospheric drying. Paper dried in a vacuum of 28, or at a temperature of about 100 F. as in my method, is very much stronger than paper dried at atmospheric presure, when the steam in the driers is at 228 F. W'hen paper is dried by my method, therefore, a cheaper furnish or stock can be used and still produce a paper equal in strength to atmospheric dried paper, in which a higher grade) furnish or stock can be used and still produce a paper equal in strength to atmospheric dried paper, in which a higher grade furnish or stock is used. In making newsprint paper, I am able to dispense with a considerable portion, of the more expensive sulphite pulp, as this can be replaced with the cheaper ground wood pulp, By my method I also reduce the the number of breaks in the web as it passes over the cylinder.

-Furthermore, in my method tliere is a vacuum chamber, and conducted away to the condenser. The operating room is free from steam, humidity and heat, andfans, and exhausters are dispensed with. In the use of my method the apparatus is at all times operating under definite humidity, the control of the drying can be closely standardized, and the moisture content in the paper carefully regulated. Some of the modern open air dryers are equipped with a blower system by which air, either heated or not, is blown through the dryer section, which will lower the temperatureat which the water is evaporated from the paper much below 212 F. and may, in some cases, reduce the temperature of evaporation as low as 180 F. or lower. p a

Having pointed out the many advantages of-my method and apparatus over those heretofore used, it will be apparent that the use of my invention results in great economy in the initial cost of apparatus and in large savings in cost of operation, maintenance and repairs.

Having thusdescribed this invention in connection with an illustrative embodiment thereof, to the details of which I do not desire to be limited, what is claimed as new and What is desired tosecure by Letters Patent is set forth in the appended claims.

\Vhat- I claim is 1. In a vacuum apparatus the combination of a vacuum chamber having one or more openings for the admission and withdrawal of material into and from said vacuum chamber to be treated, said opening or openings being sealed by one or more velocity fluid static seals, the static head of the sea s supplementing the velocity of the fluid so that together the velocity of the fluid and the static head of the fluid, balance the par- .ticular degree of vacuum maintained in the.

vacuumv chamber. 7

2. In a vacuum apparatus the combination of' a vacuum chamber, a felt roll housing, means forming a passage arranged at an angle to the horizontal and connecting the felt roll housing and'the vacuum chamber to cause a sealing fluid to have more or less static head, a sealing fluid, and means to pump said fluid into the seal at a sufiicient velocity which, added to the static head maintained in the passage connecting the felt roll housing. and the vacuum chamber. will balance the particular degree of vacuum maintained in said'vac-uum chamber.

3. In a vacuum apparatus the combination of a vacuum chamber, a felt roll housing, means forming a passage arranged at an angle to the horizontal and connecting the felt roll housing and the vacuum chamber to cause a sealing fluid to have more or less static head,'said passage having a restricted area, a sealing fluid, and means to pump said fluid into the seal at a sufficient velocity which, added to the static head maintained in the passage connecting the felt roll housing and the vacuum chamber, will balance the particular degree of vacuum maintained in said vacuum chamber.

4:. The method of sealing against the admission of air into a vacuum chamber having openings for the passage of material to be treated in said chamber, consisting in preventing the admission of air through said openings by balancing the external atmospheric pressure by a combined static and velocity fluid seal.

5. The method of continuously drying paper consisting in continuously feeding it into and out of a vacuum chamber having openings for the passage of said paper, consisting in preventing the admission ofair through said openings by balancing the external atmospheric pressure by combined static and velocity fluid seals, and drying the paper in the vacuum chamber.

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